Benzothioxanthone compounds are known for imparting color to certain plastic materials such as polymethylmethacrylates, polycarbonate, polystyrene, and polyester. The compounds are described, for example, in FR 2,124,384, DE-A 2,613,493, DE-A 2,815,031, IT 1,061,813 and in Dyes and Pigments Vol. 3, (1982) pp. 59-69. Their preparation is described in DE-B 2,134,517 and DE-B 2,134,518.
In particular, 14H-anthra[2,1,9-mna]thioxanthene-14-one compounds are described by Carlini et al. in Dyes and Pigments Vol. 3 (1982), pp. 59-69. One known photostable fluorescent colorant described by Carlini is 6-methoxy-14H-anthra[2,1,9-mna]thioxanthene-14-one. However, this colorant has the disadvantage of being poorly soluble in many of the polymers used to make coatings and films for traffic sheeting.